Multiple Sclerosis (MS) is the most common chronic inflammatory disease of the central nervous system (CNS) in the Western world and a major cause of sustained neurological disability of young adults (Compston A, Coles A. Multiple sclerosis. Lancet 2002; 359:1221-1231). The disease is characterized by destruction of myelin, associated with death of oligodendrocytes and axonal loss. One of the mechanistic hallmarks of the disease is the influx of activated T lymphocytes and other immune cells from the blood stream into brain tissue, thereby passing the blood brain barrier (BBB) (Engelhardt B, Ransohoff R M. The ins and outs of T-lymphocyte trafficking to the CNS: anatomical sites and molecular mechanisms. Trends Immunol 2005; 26:485-495). Regarding the underlying molecular mechanisms, antibodies binding α4-integrin and, thus, blocking the α4β1 dimer on T lymphocytes were shown to prevent the intrusion of immune cells into the brain in an animal model of MS, experimental autoimmune encephalomyelitis (EAE) (Yednock T A, Cannon C, Fritz L C et al. Prevention of Experimental Autoimmune Encephalomyelitis by Antibodies Against Alpha-4-Beta-1 Integrin. Nature 1992; 356:63-66 and Baron J L, Madri J A, Ruddle N H et al. Surface expression of alpha 4 integrin by CD4 T cells is required for their entry into brain parenchyma. J Exp Med 1993; 177:57-68). The neurological symptoms that characterize MS include complete or partial vision loss, diplopia, sensory symptoms, motor weakness that can worsen to complete paralysis, bladder dysfunction and cognitive deficits, which eventually may lead to a significant disability. The associated multiple inflammatory foci lead to myelin destruction, plaques of demyelination, gliosis and axonal loss within the brain and spinal cord and are the reasons contribute to the clinical manifestations of neurological disability.
There are a number of drugs known which are used in the treatment of MS. Monthly infusions of natalizumab (Tysabri®), for example, were shown to profoundly reduce the risk of relapses in MS (Polman C H, O'Connor P W, Havrdova E et al. A randomized, placebo-controlled trial of natalizumab for relapsing multiple sclerosis. New England Journal of Medicine 2006; 354:899-910) and represent a powerful therapy option in MS.
Natalizumab is a humanized monoclonal antibody against the cellular adhesion molecule α4-integrin. The drug works by reducing the ability of inflammatory immune cells to attach to and pass through the cell layers lining the intestines and blood-brain barrier. Natalizumab has proven effective in treating the symptoms of MS, preventing relapse, vision loss, cognitive decline and significantly improving quality of life in people with multiple sclerosis. It is, however, also associated with the potentially lethal adverse effects, namely the JC virus infection of the CNS, progressive multifocal encephalopathy (PML).
Monitoring of MS is necessary in order to evaluate the course of said disease. Monitoring of MS treatment is also very important in order to evaluate the efficacy or non-efficacy of a drug application. However, MS or the treatment of MS is often difficult to monitor in human patients with less capacity to communicate, e.g. mentally disabled persons. In addition, animals as patients can not speak and only communicate in an acoustical language (if at all). Further, there is often difficulty of objectively monitoring and staging MS as even descriptions of persons able to describe their symptoms are subjective. Furthermore, neurophysiological examinations are very time consuming. In addition, imaging examinations such as magnetic resonance imaging to evaluate the outcome of a MS therapy are very expensive. Moreover, before a successful MS therapy is visible on a physiological level time passes. This is problematic as drugs for MS therapy are very expensive.
Thus, there is a need for new, alternative ways of monitoring MS, particularly MS treatment, which are independent from the patient's reasoning. There is also a need for easy, save and fast methods for determining whether patients respond to a therapeutic treatment of MS or not and methods for adjusting the dose of drugs applied for treating MS in patients. Further, methods which allow the prediction of a single patient's potential risk, for example, to experience a relapse in MS, are highly desirable.
Today, biomarkers such as microRNAs (miRNAs) play a key role in early diagnosis, monitoring, risk stratification, and therapeutic management of various diseases. MiRNAs are small 15 to 27 nucleotide non-coding, highly preserved RNA molecules that recently emerged as key epigenetic regulators in a plethora of cellular pathways (Ambros V. The functions of animal microRNAs. Nature 2004; 431:350-355 and Bartel D P. MicroRNAs: Genomics, biogenesis, mechanism, and function. Cell 2004; 116:281-297). Utilizing a specialized molecular machinery, they bind complementarily to the 3′ UTR of a messenger RNA, thus preventing it from translation and leading to its degradation. It is estimated that at least a third of all genes are post-transcriptionally regulated in a miRNA-dependent manner (Lewis B P, Burge C B, Bartel D P. Conserved seed pairing, often flanked by adenosines, indicates that thousands of human genes are microRNA targets. Cell 2005; 120:15-20). Some miRNAs are genomically organized as a cluster, meaning a certain number of miRNAs are transcribed simultaneously. Other miRNAs have very similar sequences and overlapping functions and are often grouped together in miRNAs families. Increasing evidence shows that miRNAs play an indispensable role in immune functions and mechanisms of autoimmunity (Baltimore D, Boldin M P, O'Connell R M et al. MicroRNAs: new regulators of immune cell development and function. Nature Immunology 2008; 9:839-845). Indeed, cross-sectional studies investigating the peripheral blood (Otaegui D, Baranzini S E, Armananzas R et al. Differential Micro RNA Expression in PBMC from Multiple Sclerosis Patients. Plos One 2009; 4; Keller A, Leidinger P, Lange J et al. Multiple sclerosis: microRNA expression profiles accurately differentiate patients with relapsing-remitting disease from healthy controls. PLoS One 2009; 4:e7440; Lindberg R L P, Hoffmann F, Mehling M et al. Altered expression of miR-17-5p in CD4(+) lymphocytes of relapsing-remitting multiple sclerosis patients. European Journal of Immunology 2010; 40:888-898; Cox M B, Cairns M J, Gandhi K S et al. MicroRNAs miR-17 and miR-20a Inhibit T Cell Activation Genes and Are Under-Expressed in MS Whole Blood. Plos One 2010; 5; De S G, Ferracin M, Biondani A et al. Altered miRNA expression in T regulatory cells in course of multiple sclerosis. J Neuroimmunol 2010; 226:165-171; Guerau-de-Arellano M, Smith K M, Godlewski J et al. Micro-RNA dysregulation in multiple sclerosis favours pro-inflammatory T-cell-mediated autoimmunity. Brain 2011) or inflammatory CNS lesions (Junker A, Krumbholz M, Eisele S et al. MicroRNA profiling of multiple sclerosis lesions identifies modulators of the regulatory protein CD47. Brain 2009; 132:3342-3352) showed dysregulated miRNA patterns in MS.
The inventors of the present invention assessed the expression of miRNAs in patients suffering from relapsing-remitting multiple sclerosis (RR-MS). They identified new miRNAs which are deregulated between RR-MS patients and healthy controls. Said miRNAs allow monitoring of MS, particularly RR-MS. Using a combined longitudinal and cross-sectional approach in RR-MS and confirmatory animal experiments, the inventors of the present invention found that the drug natalizumab has an impact on several miRNAs in RR-MS patients. Said miRNAs allow the monitoring of MS treatment, particularly RR-MS treatment. In particular, said miRNAs represent novel targets for drug response monitoring. Moreover, said miRNAs are tools for the identification of new compounds suitable for the treatment of multiple sclerosis, particularly RR-MS.